The present invention relates to a plasma display panel of a surface discharge type having a plurality of display electrodes constituting sustain discharge electrode pairs arranged adjacent to each other.
The plasma display panel is attracting attention as a display device of wall type, and a vigorous effort is under way for improving the image quality by improving the resolution and suppressing the power consumption.
First, an explanation will be given of the structure of an AC-driven 3-electrode plasma display panel of a surface discharge type (hereinafter referred to as PDP). FIG. 1 is a perspective view showing a part of the PDP. As shown in FIG. 1, display electrodes (also called sustain electrodes) X, Y for generating the surface discharge along the surface of a substrate are arranged, at the rate of a pair on each row L of the matrix display, on the inner surface of a front substrate 100 of a transparent glass material. The display electrodes X, Y, are formed by photolithography and, as described in detail later, are each configured with a transparent electrode 102 and a bus electrode 103 of a metal thin film of a multilayer structure. In order to cover the display electrodes X, Y and the discharge space, a dielectric layer 104 for AC drive is formed by screen printing. A protective film 105 of MgO (magnesium oxide) is deposited by evaporation on the surface of the dielectric layer 104.
On the other hand, a plurality of address electrodes 106 for generating the address discharge are arranged at a predetermined pitch at right angles to the display electrodes X, Y on the inner surface of the back substrate 101. The address electrodes 106 are also formed by photolithography and are made of a metal film of a multilayer structure like the bus electrodes 103. A dielectric layer 107 is formed by screen printing over the whole surface of the back substrate 101 including the address electrodes 106. Linear partitioning walls 108 about 150 xcexcm tall, one each between each pair of the address electrodes 106, are formed on the dielectric layer 107. Phosphor bands 110 of the three primary colors R (red), G (green), B (blue) for full color display are formed, by screen printing, in such a manner as to cover the surface of the dielectric layer 107 and the sides of the partitioning walls 108 above the address electrodes 106. Also, a discharge gas such as Nexe2x80x94Xe (a mixed gas of Ne and Xe) for exciting the phosphor material by radiating ultraviolet light at the time of discharge is sealed in the discharge space 109 under the pressure of about several tens of KPa (several hundred torr). A seal member 111 is formed along the peripheral edge of the substrates for sealing the discharge space 109. The front substrate 100 and the back substrate 101 are formed separately from each other, are attached to each other and are fixed by the seal member 111, thus completing the PDP.
FIGS. 2A and 2B are a plan view and a sectional view, respectively, showing the structure of the display electrodes of the conventional PDP. The same component parts as the corresponding parts in FIG. 1 are designated by the same reference numerals, respectively. As explained with reference to FIG. 1, the display electrodes X, Y constitute a pair, and are each comprised of a wide transparent electrode 102 and a narrow transparent electrode 103 as seen from FIG. 2A.
The bus electrode 103 is made of a multilayer metal such as Crxe2x80x94Cuxe2x80x94Cr taking the conductivity and the matching with the surrounding film into consideration. The transparent electrode 102 is adapted to transmit light to prevent a reduction in luminous efficacy. The bus electrodes of the multilayer metal compensate for the insufficient conductivity of the transparent electrode 102. The bus electrode 103 is arranged on the outside of each transparent electrode 102 thereby to form a luminous area 112 between the two bus electrodes 103. Each luminous area 112 is defined by the partitioning walls 108 indicated by dashed lines formed on the back substrate in opposed relation to the address electrode 106 indicated by one-dot chains in FIG. 2A.
FIG. 2B is a cross sectional view of the display electrode taken along the arrow in FIG. 2A. To complement the foregoing description with reference to FIG. 1, as shown in FIG. 2B, the transparent electrodes 102 are formed in contact with the inner surface of the front substrate 100, and the bus electrodes 103 are deposited on a part of the transparent electrodes 102, respectively. Also, though not shown in FIG. 2A, the dielectric member 104 is formed in such a manner as to cover the transparent electrodes 102 and the bus electrodes 103, and a protective film 105 is formed on the dielectric member 104.
In this structure, the main discharge is generated between the display electrodes X and Y to emit light from the portion selected by the address electrodes 106. In the light emission, the ultraviolet light generated by the discharge excites the phosphor member 110 (FIG. 1) and appears as visible light on the front substrate 100.
In recent years, the trend has been toward an increased number of pixels, to meet an HDTV requirement, at the sacrifice of increased power consumption. Specifically, a higher definition of the screen of the same size increases the number of electrodes and hence the area occupied by the electrodes, resulting in a correspondingly increased power consumption. Japanese Unexamined Patent Publication No. 8-22772 discloses a PDP in which the power consumption is suppressed by changing the pattern of the wide transparent electrode and thus the area thereof is reduced. FIG. 3 is a plan view showing the display electrode pattern for reducing the power consumption disclosed in the same publication. As shown in FIG. 3, each transparent electrode 122 of the display electrodes X, Y includes a plurality of protrusions 122a extending in the direction perpendicular to the main pattern and each having, at the forward end thereof, a discharge unit 122b of a width required for discharge. This pattern shape can reduce the area of the transparent electrodes 122 remarkably. The bus electrodes 123 are formed on the outside of the transparent electrodes 122, respectively, in the same manner as explained with reference to FIG. 2.
The discharge is generated at the opposed portions of the adjacent transparent electrodes 122. The portions defined by the partitioning walls 128 opposed to the address electrodes 126 on the back substrate constitute a luminous area 129. Therefore, the opposed portions of the transparent electrodes 122, as long as they are in a predetermined spaced relation with each other in the luminous area 129, can generate the desired discharge. In view of this, as shown in FIG. 3, a pattern formed with the discharge potions 122b having a predetermined width through the protrusions 122a, respectively, can generate a discharge without any problem. Thus, the power consumption can be reduced by reducing the area of the transparent electrodes 122.
In spite of this, it has been found that the pattern described above for reducing the area is accompanied by another problem. Specifically, in view of the fact that the transparent electrode film as thin as several thousand A may cause a disconnected portion 130 at the time of patterning under the effect of the dust or a scratch or other damage on the surface of the substrate. The disconnected portion 130 of the protrusion 122a cuts off the conduction to the discharge unit 122b and thus naturally prevents the discharge.
U.S. Ser. No. 5640068, on the other hand, discloses a PDP with the brightness increased by reducing the shielding area of the luminous area. FIG. 4 is a plan view showing a display electrode pattern for reducing the shielding area disclosed by the well-known reference. As shown in FIG. 4, each transparent electrode 142 of the display electrodes X, Y extends in parallel to the main pattern 143, and the transparent electrode 142 and the main pattern 143 are electrically connected to each other through a plurality of connecting patterns 144 extending in a direction perpendicular to the main pattern 143. The bus electrode 123, like the one explained with reference to FIG. 2, is formed on the outside of the transparent electrode 122. The connecting pattern 144, which is formed of a shielding metal material, is formed in overlapped relation with the partitioning wall 148 and therefore the luminous area 149 is not shielded. In this pattern, however, the current flows along the transparent electrodes 142 and therefore the power consumption cannot be reduced.
The object of the present invention is to provide a plasma display panel of a surface discharge type capable of generating a discharge for display positively while suppressing the power consumption to low level even with an increased number of electrodes for realizing a high definition.
According to a first aspect of the invention, there is provided a plasma display panel of a surface discharge type, comprising an discharge pattern for each luminous area corresponding to each display cell, in which each main pattern and the corresponding discharge patterns are electrically connected to each other by at least an auxiliary pattern of higher conductivity than the discharge patterns.
Specifically, the plasma display panel of a surface discharge type according to the first aspect of the invention comprises a pair of substrates arranged in opposed relation to each other with a discharge space therebetween and a plurality of display electrode pairs arranged, in proximity to each other, inside the substrates, wherein each display electrode includes a main pattern extending in one direction, a plurality of discharge patterns formed for each luminous area corresponding to a display cell, and a plurality of auxiliary patterns for electrically connecting the main pattern and the discharge patterns to each other, and wherein the auxiliary patterns are higher in conductivity than the discharge patterns.
In the first aspect of the invention, the provision of the discharge patterns at positions protruded from the main pattern in the direction at right angles to the main pattern of the display electrode can suppress the power consumption by reducing the intermediate pattern area. At the same time, the main pattern and the discharge patterns are connected to each other by the auxiliary patterns made of a material having a high conductivity, and therefore a sufficient conductivity can be secured between the main pattern and the discharge patterns.